拍出《Top Gear》风格的汽车大片

想拍出全球最畅销的汽车杂志《Top Gear》风格的精彩大片么?想要留下汽车的艺术性微距影像吗? Ed Godden向你展示如何拍出更好的汽车摄影作品。     

Circular array of outward sloping monopoles for vehicular diversityantennas

A circular array of outward-sloping monopoles is analyzed as a diversity antenna for vehicle rooftop mounting. The monopoles are assumed to approximate minimum scattering antennas, have sinusoidal current distributions, and reside on an infinite, perfectly conducting ground plane. The envelopes of the received signals are considered Rayleigh distributed. The advantage of the array configuration is that the feedpoint spacing can be made almost arbitrarily small, even for a large number of branches. A three-element array with element lengths of 0.6 wavelengths and feedpoint spacing 0.1 wavelengths operating at 463 MHz was field-tested and the results are in good agreement with the analysis     

Vascularized bone flaps versus nonvascularized bone grafts for mandibular reconstruction: an outcome analysis of primary bony union and endosseous implant success

We present a patient with a lesion of the mesial frontal cortex, including the supplementary motor areas bilaterally, who on clinical examination revealed no spontaneous movements, although neurophysiological examination indicated integrity of the corticospinal tract to thenar and tibialis anterior muscles bilaterally. The patient was alert, speech was hesitant, and he was able to move his hands only on command. The role of the supplementary motor areas in planning, setting, and execution of skillful voluntary movements has been previously established by direct cortical electrical stimulation and studies of regional cerebral blood flow. The findings in our patient support the role of the supplementary motor areas in initiating movements. The presence of motor evoked potentials after acute insults to the brain is considered to be associated with a good functional outcome. This is in contrast to our patient who did not show improvement in motor performance, despite preserved motor evoked potentials. Hence, in the case of bilateral lesions to the supplementary motor areas sparing the corticospinal tract, the presence of motor evoked potentials may not predict functional recovery.     

Molecular approaches to study probiotic bacteria

Functional foods comprising probiotic bacteria are receiving increasing attention from the scientific community and science funding agencies [1]. An essential aspect relating to the functionality of probiotic-based foods is to develop molecular methods to determine the presence, activity and viability of probiotic bacteria in the human gastrointestinal (GI) tract [2]. The GI tract is composed of a complex ecosystem of various microbial habitats colonized by numerous different commensal micro-organisms. This indigenous gut microbiota is essential to the overall health of the host by performing important physiological functions. In particular, they protect against pathogenic bacteria and drive the development of the immune system during neonatal life. Further metabolic activities of the GI microbiota that beneficially affect the host include continued degradation of food components, vitamin production, and production of short chain fatty acids that feed the colonic mucosa. It is clear that factors such as diet, sickness, stress, or medication can result in loss of well-being of the host, and it is assumed that some of these symptoms are due to perturbation of what is termed the normal balance of the gut microbiota. Knowledge of the structure and function of the standard microbiota, and its response to diet, genetic background and lifetime of the host must be taken into account when designing probiotic-based functional foods. The application of molecular techniques for detection and identification of microbes has provided a major breakthrough in the analysis of microbial ecosystems and their function [3]. The successful application and further potential of these molecular methods to study probiotic bacteria and their impact on the standard GI microbiota is discussed below.     

Recovery of Metal Working Fluids Using Chelation-Ultrafiltration Process

Metal working (MW) fluids are used to control friction and temperature, improve workpiece surface quality, and reduce tool wear. The batch-life of the MW fluid investigated was controlled primarily by the concentration of metallic soaps (complexes between the oil emulsifier and Al∕Mg. Ethylenediaminetetraacetic acid, a strong metal chelator, was added to the MW fluid to break the oil-Al∕Mg complexes. The aqueous-phase ethylenediaminetetraacetic acid-Al∕Mg complexes were then separated from the oil phase by ultrafiltration (UF). Al levels were reduced between 39 and 49%, and Mg levels were reduced between 67 and 77%. Al transfer from the oil phase to the aqueous phase was slow and increased during UF concentration. Rinsing the concentrated MW fluid with deionized water decreased the ash content but had a lesser impact on Al∕Mg removal. Al mass balances produced errors of 2.8% for run 3 and 6.2% for run 4. The UF system (0.11-μm ceramic membrane) effectively separated the oil and aqueous phases. Permeate turbidity was generally <1 nephelometric turbidity unit and permeate flux ranged from 390 to 220 L∕m2-h (230 to 130 gal.∕ft2-day) depending on the degree of concentration.     

Effects of neurotrophins on embryonic retinal outgrowth

In the literature it is generally assumed that venous reflux within the radicular veins is prevented by the presence of bicuspid valves and narrowing of the transdural part of these vessels. Recently, we performed a human cadaver study of the internal vertebral venous plexus. Surprisingly, a large number of radicular and perimedullary veins appeared to be filled with Araldite CY 221 mixture, after injection of this material into the vertebral venous system, implicating reflux via the radicular veins and suggesting insufficiency of the presumed anti-reflux mechanism. Therefore, it was decided to study the radicular veins in order to determine and to investigate the presence or absence of anti-reflux mechanisms within this system. The vertebral venous systems of ten fresh human cadavers, between 64 and 93 years of age, were injected with Araldite CY 221 mixture. After polymerization, all cadavers were dissected and the spinal nerve sheaths, including nerve roots, radicular veins and epidural veins, were excised as a whole. After macroscopical examination, serial sections (40 microm) were cut on a freezing microtome and stained in Von Gieson medium. Every third section was stained immunohistochemically with smooth muscle antigen (SMA), to visualize smooth muscle cells. In all cadavers, a number of intradural radicular veins was filled with Araldite. Employing microscopical examination, no bicuspid valves were found. However, four structures were encountered that might serve as ananti-reflux-mechanism: 1) intravenous dural folds, 2) meandrous configuration, and 3) narrowing of the radicular veins at the point of penetration of the dura mater, and 4) varying numbers of smooth muscle fibers in the walls of the intradural and extradural parts of the radicular veins. Reflux via the radicular veins seems to be a physiological phenomenon. Structural valves have not been encountered during this study. Intravenous dural folds, meandrous configuration and narrowing of the transdural part of the radicular veins, and the presence of large numbers of smooth muscle cells in the radicular venous walls suggest the existence of a dynamic reflux-regulating system that has the ability to increase the intravascular resistance under conditions of venous hyperpression, in order to protect the spinal cord from venous pressure waves. Possibly, venous reflux via the radicular veins has a role in selective cooling of the spinal cord.     

Bolus dispersal through the lungs in surfactant replacement therapy

A model is presented of surfactant replacement therapy. An instilled bolus is pushed into the lungs on the first inspiration, coating the airways with a layer of surfactant and depositing some in the alveoli. Layer thickness depends on the capillary number (muU/gamma, where mu, U, and gamma are bolus viscosity, advancing meniscus velocity, and surface tension, respectively). Larger capillary number leads to thicker layers, reducing alveolar delivery. Subsequently, surface tension gradients sweep surfactant into alveoli not receiving surfactant during the first inspiration. The effects on spreading of sorption kinetics, bolus viscosity, initial layer thickness, initial penetration of surfactant, gravity, and shear stress are examined. Sorption nearly eliminates surface tension gradients in central airways but produces a sharp transition at the leading edge of the exogenous layer. Local thinning of the liquid layer results, trapping 95% of the surfactant in the airways. Gravity and ventilation augment transport somewhat. Transport to the periphery takes 4-170 s for the leading edge but considerably longer for the bulk of the surfactant. The model demonstrates how the various physical parameters governing surfactant distribution might alter the response to surfactant replacement therapy.     

Determination by photoreduction of flip-flop kinetics of spin-labeled stearic acids across phospholipid bilayers

Spin-labeled stearic acid derivatives (N-DS) can be used to determine the rate at which lipid-derived drugs can cross a phospholipid bilayer (flip-flop). The flip-flop rate of N-DS (where N=5, 6, 7, 9, 10, 12, 16), was measured using vectorial photoreduction of nitroxides to their corresponding hydroxylamine by FMN, a charged, membrane-impermeable flavin, by hydrogen atom transfer from EDTA. From the time difference in the photoreduction rates of N-DS located in the outer and inner half of the bilayer, the flip-flop rate of N-DS across the bilayer can be determined. The results show that at pH 8.0 or lower, the photoreduction of 5-DS on one side of the membrane by FMN is slower than the flip-flop rate of 5-DS across phospholipid bilayers. For 5-DS at pH 7.0, this rate is at least 33.8+/-4.24 s or faster. Stearic acids with the spin label at different positions along the acyl chain (N=5, 6, 7, 9, 10, 12) have similar flip-flop rates in the liposomes at pH 7.0 although 16-DS is slower, probably due to the inaccessibility of the nitroxide moiety to FMN. It is most likely that the fast distribution of 5-DS in cells is due to the fast movement of acidic form, but not the salt form, of 5-DS across membrane bilayers. The oxazolidine (nitroxide moiety) does not seem to affect the pKa ( approximately 8.3) of stearic acid at air-water interface. Thus, N-DS are good probes for studying the distribution kinetics of stearic acid derivatives in biological systems.